Posted By
JamesC
on 2005-12-26
16:58:48
|  1551 Troubleshooting Advice
Good day, everyone!
I finally found time to test the 1551s that I have received in the last few months..... the two I received from Plus4Vampyre work just fine (suprising, considering the case of one is in several pieces).
However the one I received from Peter (The Plus/4 King, via Chris of commodore16.com) acts very weird. I should note that this is the only one that has a 8/9 switch added on the back.
No matter what I set the switch to, this 1551 will not respond. No DIRECTORY U8 or U9, no ?DS$, nothing. I plugged in a Script/Plus cartridge and after reseating the 1551's paddle several times, the cartridge would work. (Previous attempts showed the cartirdge to lock the system after pressing F2, or the screen would go all PAL-like, and with my NTSC setup that's not a good thing).
Without the cartridge, only this 1551 plugged in, the first few tests caused the computer to go straight to MONITOR without completely initializing BASIC. I got the topline with free bytes, but no function key list. It was as if the function ROM test routine was executing improperly.
Has anyone else come across a 1551 that acted this way, and what did you do to repair it?
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Posted By
JamesC
on 2005-12-26
17:04:35
| Re: 1551 Troubleshooting Advice
A side note.... all three 1551s were tested on the same electrical setup (110 to 220 step-up transformer outputting 220V 40W). I used the same power cord for all three drives.
Chris --> still haven't seen any power cords. Can you verify when they were sent, and follow up with UK postal?
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Posted By
Chris
on 2005-12-27
05:40:06
| Re: 1551 Troubleshooting Advice
Hi James,
The problem with the 1551 sounds very strange, I can't help with a fix but can assure you I tested the 1551 before I sent it over to you.
The power cable was sent months ago, I thought you had recieved it by now as I've cleared my wallet of reciepts and shredded them. I would be happy to post another one over to you in the new year, as it didnt cost alot to post. I still have your address within my emails somewhere.
Chris 
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Posted By
SVS
on 2005-12-27
08:21:28
 | Re: 1551 Troubleshooting Advice
James, be informed that a 1551 set as unit #9 works ONLY if another 1551 is connected and set as unit #8.
If you're sure about the AC power, I fear the IC of the cartridge is gone... 
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Posted By
JamesC
on 2005-12-28
11:44:19
| Re: 1551 Troubleshooting Advice
Bumping this thread...
I don't see the point of an 8/9 switch if the drives can assign their own drive number. I look at the motherboard and the English manual, and I see the jumper to cut like on a 1541 drive.
Bo Zimmers agrees that the drives can assign their own number on this page: Bo's 1551 Page, which is different than someone (I don't remember who) told me about thet 1551 needing to be told what unit number (8 or 9) it is to be.
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Posted By
SVS
on 2005-12-28
11:55:53
| Re: 1551 Troubleshooting Advice
>>>... the drives can assign their own number
Do you mean that the number assignment could be automatic by drive-OS ?
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Posted By
JamesC
on 2005-12-28
12:14:02
| Re: 1551 Troubleshooting Advice
>Do you mean that the number assignment could be automatic by drive-OS ?
Yes. it is my understanding that two 1551s, fresh from original package (no modifications) can be plugged into the Plus/4 and assign their own device numbers. The one plugged into the Plus/4 would be device 8, and the one plugged into device 8's paddle would be device 9.
I presume that 8 has to be powered before 9 will be 9, otherwise 9 would be 8....
In this case, an 8/9 switch is not necessary ....... unless one has a 1541 that they need to be 8, and the 1551 as 9. In this case the switch would be needed to prevent the 1551 from taking over as 8.
I think I just answered my own question.
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Posted By
The +4 King
on 2005-12-28
19:08:39
 | Re: 1551 Troubleshooting Advice
Hi James
The Reason that i put the Switch on to the 1551 is that i was running a 1541 & a 1551 at the same time & that i wanted to swop Software beween the both. I found that it worked fine for me 
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Posted By
SVS
on 2005-12-29
02:27:36
| Re: 1551 Troubleshooting Advice
I should not attempt to connect the second 1551 while the first one is powered on... :-/
The most critic IC is just on the paddle cartridge, as well known.
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Posted By
JamesC
on 2006-01-01
20:06:15
| Re: 1551 Troubleshooting Advice
@SVS: I know to turn off all power before plugging/unplugging anything.
@all: Here's a new one: I was going through my Plus/4s today to see which ones work and which ones do not work..... the first 4 Plussys work just fine with one of the working 1551s.
But the Canadian-logo unit has fits with the 1551! I can do a ?DS$ and get "73, CBM DOS 2.6TDISK", and then immediately do a DIRECTORY and get no response! The computer goes straight to the READY prompt. A DS$ at this point gives "00, OK" but the 1551 activity light is still on from the DIRECTORY request!
I opened it up and the chips are all newer chips. Kernal is Revision 5. Just for the heck of it, I dropped a Revision 4 Kernal into it. Now it does partial directories with a random number on the first line of the disk directory (instead of a 0 before the disk name) and the first line is not reversed.
And about one in three DIRECTORY requests gets cut off, but then shows blocks free.
Now, how is THAT for strange problems?
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Posted By
Chicken
on 2007-03-19
17:00:23
 | Re: 1551 Troubleshooting Advice
http://www.zimmers.net/cbmpics/d1551.html
"When connected to the Plus/4, each 1551 drive has the amazing capability of assigning its own device number (8 or 9), allowing the user to attach up to two 1551s to a single Plus/4."
While the latter is true, I can't confirm that the drive is able to assign its own device number.
Has anyone else checked this? Owning two 1551s is probably quite decadent
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Posted By
Chicken
on 2007-03-20
08:05:07
| Re: 1551 Troubleshooting Advice
I double checked this because it would have been a cool feature of which I had never heard before. It doesn't matter which drive you turn on first, if you have two (unmodified, therefore device number 8) 1551s connected to the plus/4, neither one is working like it should. And there's no device number 9 present.
Conclusion: You either have to cut the trace (jp1, if I remember correctly) on the board to turn one 1551 into a permanent drive 9 or switch on just one drive (doesn't matter if it's the first one connected to the expansion port or the second one) and set it to device number 9 by software and then switch on the other drive. Of course that setting will only last until the next reset.
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Posted By
SVS
on 2007-03-20
13:19:26
| Re: 1551 Troubleshooting Advice
Well I'm one that has 2 1551s online )
What Chicken says is correct. Only the expansion port inserting order could be interchangeable. The drives continue to be *both* no. 8 if not set by user.
Another interesting thing is that a 1551 set as device #9 cannot work alone (without another 1551 set as device #8).
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